You should only ever have ONE DHCP server on a network. A number of devices you list CAN Offer that service in its config. Just say NO

My Snology CAN be the DHCP, My Access Point CAN be the DHCP. But I leave that job to my Router.
For 99% of home user, the ROUTER is the DHCP server.
OTOH , the DNS service to use, could be set at each device (manual). (not usually if DHCP is used). DNS problems usually result in the 'Taking to long to Respond'/'Address Not Found' on web pages or Pings failing.